1. Field of the Invention
The present invention relates to an apparatus and method for accurately securing an airway for the purposes of endotracheal intubation of a patient. The apparatus includes a flexible, directionally steerable probe having multiple gas-aspirating ports connected to a like number of infra red gas analyzers which are in turn graphically displayed on a monitor of an available desk or personal computer ("PC") as wave-forms (or "capnograms") indicative of the strength or concentration of the analyzed gas. The gas usually analyzed is carbon dioxide (CO.sub.2) which, of course, is the dominant gas from normal respiration exhaled through a patient's airway. By comparing the relative strength of the CO.sub.2 wave forms/capnograms, the operator can steer the flexible probe in the direction of the dominant concentration of CO.sub.2 and thereby accurately locate and secure the patient's airway.
2. Background of the Invention
More particularly, the apparatus of the present invention is a capnography assisted stylet for endotracheal intubation to secure an airway.
In medical terminology the term "airway" has two somewhat different meanings. When we talk about an airway as a device, we meant a short piece of pipe inserted into the mouth or nose and its purpose is to bypass the tongue which can flop down and partially or even totally obstruct ventilation. These devices are only partial airways and they usually are disposable and of very little cost since it is generally a piece of inexpensive molded plastic or rubber.
The medical field also frequently talks about "gaining control of the airway" or "losing the airway." When "airway" is used in this fashion, what is meant is the ability to pass a tube from the outside all the way into the trachea. In adults, this would include the additional act or step of inflating a balloon to form a seal between the outer wall of the tube and the tracheal wall so that there is no leakage, thus allowing positive pressure ventilation and preventing the entry of undesired matters, such as gastric acid, into the airway. Tracheostomy is one way of controlling the airway, but it is usually done only in emergencies when there is insufficient time for less traumatic or invasive means (e.g., otherwise the patient may die).
To "lose the airway" means that (1) it is not possible to place the tube in the trachea and (2) the patient cannot breathe, either because something is obstructing their air passage or because of some physiologic event such as muscle paralysis or central nervous disorder or brain damage. If the patient cannot breathe and you cannot artificially breathe for him, then it is said you have lost control of the airway.
Endotracheal intubation is usually performed by anesthetists (doctors or nurses) because they do it everyday and are generally the most experienced in endotracheal intubation. It is also performed by paramedics and emergency room personnel when they feel that the patient is about to lose the airway and there are no anesthetists available. In most patients, under controlled (e.g., elective) conditions, the airway can be secured (intubated) fairly easily. However, in about five percent (5.0%) of cases, control of the airway can be difficult to gain or achieve, either because of unusual airway anatomy of the patient or the anatomy is distorted by trauma (e.g., a cancerous growth or other pathologic obstruction). Also, in some situations it is not prudent to manipulate the patient's neck for intubation. For example, if a patient has cervical spine injury and has a neck collar on, when one attempts to extend the patient's neck, there is a greatly increased risk of further damage to the spinal cord.
When all else fails, an emergency tracheostomy will have to be performed or the patient will lose the airway, interrupting breathing and resulting in serious consequences or even possibly death. Virtually all anesthesia departments in this country have some kind of "difficult airway cart" containing various devices to help gain control of a difficult airway. A frequently used device is the fiber-optic bronchoscope that permits the operator to visually "navigate" the airway and lead to the trachea to slip an endotracheal tube therein for intubation. There are many shortcomings of such fiber-optic scopes: they use coherent fibers and thus are quite expensive; they are difficult to operate and not all anesthesia personnel are trained in their use; the fibers have a tendency to break after use; the fiber optic lens can get dislocated requiring high repair costs; and sometimes secretion and blood in the airway can totally obscure the visual field.
Another method (frequently discussed but in my experience almost never used) is retrograde intubation. A hole is punctured at the neck into the trachea and a long wire is passed back into the mouth. One end of the wire is anchored at the neck and the other is pulled out the mouth and an endotracheal tube is slipped over it into the trachea. Even this seemingly direct technique can result in "hang ups" in an abnormal airway. Further, proper use of this device is often time-consuming, and if one is going to devote significant time using this device, it is often more expedient to perform a tracheostomy and gain control of the airway much more quickly.
One further method is trans-tracheal jet ventilation. In this procedure, the patient's neck is punctured and a small tube is inserted into the trachea. This tube allows a high pressure jet stream of oxygen to be delivered to the lungs. At that point, however, the airway is only partially secured and often the principal result obtained by using this device is to gain additional time to insert a proper endotracheal tube. In my practice, I use this technique frequently for difficult airways. However, the availability of approved trans-tracheal jet ventilation devices is problematic. There is a manual jet, called Sander's jet, that is nothing more than a hand operated air valve which is very difficult to operate at the rate needed for effective intubation (over 120 breaths per minute).
Finally, it is appropriate in this background section to mention intubating stylets. An intubating stylet is a long malleable rod which the anesthetist molds into a form predicted to conform to the shape of the patient's airway. After molding the stylet into the predicted shape, the anesthetist then inserts the formed stylet through the patient's mouth hoping that it will be directed to the trachea. Of course, this is often nothing more than a blind insertion and if the stylet has not been molded into a conforming shape, it will not be operationally successful. In this situation, the stylet must be withdrawn, remolded and reinserted until the trachea is located. Given that a difficult airway is almost by definition one that does not conform to a normal anatomy, this method is often futile. Nevertheless, the prior art shows much activity in trying to improve this type of device.